TPU Foams

Title: POLYURETHANE FOAMS AND METHOD FOR PRODUCING SAME

Number/Link: US2017/0174818

Applicant/Assignee: Lubrizol

Publication Date: 22-june-2016 (PCT oct. 2015)

“Gist”: TPUs with specific MW and polydispersity are injection moulded together with cellopener and gas in supercritical state

Why it is interesting: The invention relates to injection moulded “flexible foams”, especially useful for footwear applications. Thermoplastic polyurethanes with a Mw of 120,000 to 500,000 and a dispersity index of 1.85 to 2.51 are foamed using a gaseous blowing agent (CO2 or C1 to C6 hydrocarbons etc. ) together with a cellopener (silicone or EO/PO surfactant), such that at least 50% of cells are open.  In the examples the blowing agent is added in supercritical state to the melt before injection moulding. The type of gas used, nor the densities of the foams are mentioned.  Foaming TPU with gas in supercitical has also been file by Nike as discussed before in this blog.

Nike shoe with foamed thermoplastic midsole

 

Low Density Foamed TPU

Patent Title: FOAMED THERMOPLASTIC POLYURETHANE AND MICROWAVE MOLDED ARTICLE THEREOF

 Number/Link: US2017/0073490

Applicant/Assignee: Sunko Ink; Tayin R&D

Publication date: 16-mar-2017

Gist”: Blown TPU pellets are subjected to a second foaming process using microwaves

Why it is interesting: Thermoplastic polyurethane is extruded together with an excess of blowing agent using a single screw extruder and a pelletizer. The foamed pellets are then put in a mould together with water and subjected to microwave radiation which causes the pellets to expand and sinter into a moulded part. In the examples expandable microspheres are used as blowing agent in amounts of 5 to 25 php of TPU. The pellets are irradiated for 20 to 180 s at a power of up to 5000 W. Moulded densities as low as 170 kg/m³ are achieved.

SEM picture of moulded TPU according to the invention

 

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